public class Demo1 {
    private static int count = 0;
    public static void main1(String[] args) throws InterruptedException {
        Object locker = new Object();
        Thread t1 = new Thread(() -> {
            for (int i = 0; i < 5000; i++) {
                synchronized (locker) {
                    count++;
                }
            }
        });
        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 5000; i++) {
                synchronized (locker) {
                    count++;
                }
            }
        });

        t1.start();
        t2.start();
        t1.join();
        t2.join();

        System.out.println("count = " + count);
    }

    public static void main(String[] args) throws InterruptedException {
        Object locker1 = new Object();
        Object locker2 = new Object();
        Object locker3 = new Object();

        Thread t1 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (locker1) {
                    try {
                        locker1.wait();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                }
                System.out.print('A');
                synchronized (locker2) {
                    locker2.notify();
                }
            }
        });

        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (locker2) {
                    try {
                        locker2.wait();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                }
                System.out.print('B');
                synchronized (locker3) {
                    locker3.notify();
                }
            }
        });

        Thread t3 = new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                synchronized (locker3) {
                    try {
                        locker3.wait();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                }
                System.out.println('C');
                synchronized (locker1) {
                    locker1.notify();
                }
            }
        });

        t1.start();
        t2.start();
        t3.start();

        Thread.sleep(1000);

        synchronized (locker1) {
            locker1.notify();
        }
    }
}
